Nowadays, wire network is greatly advanced and widely applied. However, it is not visual to dispose a lot of wires indoors. Furthermore, it is inconvenient to dispose the wires. Moreover, the wires occupy indoor space. To encounter the above problems, wireless network is developed. A conventional wireless local area network (WLAN) adopts IEEE802.11 wireless communication protocol and transmits data through frame. When a wireless network device connected with a computer transmits data through radio wave, the data are transmitted to a buffer of the wireless network device before the data are transmitted, and then the data are transmitted to the network through the buffer after the data are completely transmitted to the buffer.
In addition, a conventional wireless network device with QOS requires real time and different-categoried data. The different categories of data have different priority. So the network device transmits the data according to the priority of the data. The network device has a limited storing capacity and cannot store all categories of data at the same time. Therefore, when the required data are not stored at the network device, the data should be rapidly transmitted from a host system. However, transmission operation of the conventional network device cannot be activated until the data are completely transmitted to the buffer of the network device. So the conventional network device cannot meet the requirement of real time QOS transmission.